Synthesis and characterisation of luminescent fluorinated organoboron compounds

The reaction of 8-hydroxyquinoline (HQ) with B(C6F5)(3) leads to the formation of the zwitterionic compound (C6F5)(3)BQH (1), involving a proton migration from O to N. Compound 1 can be converted thermally to (C6F5)(2)BQ (2), which can also be prepared from (C6F5)(2)BCl and HQ. The reaction of HQ with (C6F5)B(OC6F5)(2) generates initially (C6F5)(OC6F5) BQ (3), which easily hydrolyses to give the diboron compound ((C6F5) BQ)(2)O (4). Compounds 1, 2 and 4 have been fully characterised, including X-ray analysis. The spectroscopic properties of these compounds, including photoluminescence (PL) have been investigated and compared with the non-fluorinated luminescent boron compound (C6H5)(2)BQ and also with AlQ(3). The changes in luminescent behaviour upon fluorination of these boron quinolinate compounds have been rationalised using computational studies.